U.S. Pat. No. 4,152,953 issued in the name of Headley discloses a roller valve lifter having a roller and shaft assembly received in the open, bottom end of the lifter body. The roller assembly includes an anti-rotation plate which engages a slot in the cam face to prevent rotation of the follower, relative to the surface of the cam, during operation. The design, while effective, requires that the lifter carry the anti-rotation assembly as part of the roller and shaft, significantly increasing the reciprocating mass of the follower.
U.S. Pat. No. 5,361,733 issued in the name of Spath et al, discloses a roller hydraulic valve lifter (RHVL) having dual roller shaft assemblies. Rotation of the valve lifter is prevented through an extended roller shaft which engages a slot in the engine head bore in which the lifter is disposed. The slot requires modification of the engine head for application of the lifter.